Antenna switching in multiple radio terminal

Abstract

In a multiple portable phone, a first antenna is provided for a first communication system, a second antenna is provided in common to the first communication system and a second communication system. A switching circuit is controlled based on a control signal. A receiving circuit for the first communication system is connected to one of the first and second antennas via the switching circuit. A transmitting and receiving circuit provided for the second communication system is connected to the second antenna. A control unit generates the control signal to control the switching circuit to connect the impedance matching circuit to a path from the second antenna to the transmitting and receiving circuit when the transmitting and receiving circuit carries out a receiving operation using the second antenna while the receiving circuit carries out a receiving operation using the first antenna.

What is claimed is:  
     
       1. A multiple portable phone comprising: 
       a first antenna for a first communication system;  
       a second antenna common to said first communication system and a second communication system;  
       a switching circuit controlled based on a control signal;  
       a receiving circuit provided for said first communication system, and connectable to said first and second antennas via said switching circuit;  
       a transmitting and receiving circuit provided for said second communication system, and connectable to said second antenna;  
       an impedance matching circuit connected to said switching circuit; and  
       a control unit generating said control signal to control said switching circuit to connect said impedance matching circuit to a path from said second antenna to said transmitting and receiving circuit when said transmitting and receiving circuit carries out a receiving operation using said second antenna while said receiving circuit carries out a receiving operation using said first antenna.  
     
     
       2. The multiple portable phone according to  claim 1 , further comprising a common filter of a low pass filter and a band pass filter, and wherein said receiving circuit is connected to said second antenna via said switching circuit and said low pass filter in response to said control signal, and said transmitting and receiving circuit is connected to said second antenna via said band pass filter. 
     
     
       3. The multiple portable phone according to  claim 1 , wherein said control unit controls said receiving circuit while generating said control signal, such that said receiving circuit carries out an intermittent receiving operation in a first predetermined time interval as said receiving operation while one of said first and second antennas is selected. 
     
     
       4. The multiple portable phone according to  claim 3 , wherein said control unit controls said transmitting and receiving circuit while generating said control signal, such that said transmitting and receiving circuit carries out an intermittent receiving operation in a second predetermined time interval as said receiving operation using said second antenna. 
     
     
       5. The multiple portable phone according to  claim 4 , wherein said control unit controls said intermittent receiving operation of said receiving circuit and said intermittent receiving operation of said transmitting and receiving circuit to be independent and asynchronous. 
     
     
       6. The multiple portable phone according to  claim 1 , further comprising a transmitting circuit provided for said first communication system, and connectable to said first and second antennas via said switching circuit, and 
       wherein said switching circuit comprises:  
       first and second switches operatively connectable said receiving circuit to said first antenna;  
       third and fourth switches operatively connectable said transmitting circuit to said first antenna via said first switch, wherein a node between said third and fourth switches is operatively connected to said second antenna; and  
       a fifth switch operatively connectable said impedance matching circuit to said second antenna via said first switch,  
       wherein said first to fifth switches are controlled in response to said control signal.  
     
     
       7. The multiple portable phone according to  claim 6 , wherein said switching circuit further comprises: 
       a sixth switch connected between a first external terminal and a node between said second switch and said receiving circuit, and  
       wherein said sixth switch is controlled in response to said control signal.  
     
     
       8. The multiple portable phone according to  claim 6 , wherein said switching circuit further comprises: 
       a seventh switch connected between a second external terminal and the node between said second switch and said receiving circuit; and  
       an eighth switch connected between said second external terminal and a node between said fourth switch and said transmitting circuit, and  
       wherein said sixth to eighth switches are controlled in response to said control signal.  
     
     
       9. The multiple portable phone according to  claim 1 , wherein said impedance matching circuit has substantially the same impedance as the receiving circuit. 
     
     
       10. The multiple portable phone according to  claim 1 , wherein said first communication system is a PDC system and said second communication system is a PHS system. 
     
     
       11. The multiple portable phone according to  claim 1 , wherein said first antenna is built in said phone. 
     
     
       12. An antenna switching method in a multiple portable phone, said method comprising: 
       (a) selectively connecting a receiving circuit for a first communication system to one of a first antenna and a second antenna via a switching circuit for a receiving operation of said receiving circuit;  
       (b) connecting a transmitting and receiving circuit for a second communication system to said second antenna for a receiving operation of said transmitting and receiving circuit; and  
       (c) compensating impedance change depending on said switching circuit, wherein said (c) step includes:  
       connecting said impedance matching circuit to said path from said second antenna to said transmitting and receiving circuit when said transmitting and receiving circuit carries out said receiving operation using said second antenna while said receiving circuit carries out said receiving operation using said first antenna.  
     
     
       13. The method according to  claim 12 , wherein said (a) step includes: 
       connecting said receiving circuit to said second antenna via said switching circuit and a low pass filter, and  
       said (b) step includes:  
       connecting said transmitting and receiving circuit to said second antenna via a band pass filter.  
     
     
       14. The method according to  claim 12 , wherein said receiving operation of said receiving circuit is an intermittent receiving operation in a first predetermined time interval while one of said first and second antennas is selected. 
     
     
       15. The method according to  claim 14 , wherein said receiving operation of said transmitting and receiving circuit is an intermittent receiving operation in a second predetermined time interval using said second antenna. 
     
     
       16. The method according to  claim 15 , wherein said intermittent receiving operation of said receiving circuit and said intermittent receiving operation of said transmitting and receiving circuit are independent from each other and asynchronous with each other. 
     
     
       17. The method according to  claim 12 , wherein said impedance matching circuit has substantially the same impedance as the receiving circuit. 
     
     
       18. The method according to  claim 12 , wherein said first communication system is a PDC system and said second communication system is a PHS system.